feat(detail): full-screen event detail (S4) with humanized recurrence

Tapping an event in the week/day timeline opens a full-screen detail
destination (MD3 list→detail, not a bottom sheet) overlaying the calendar
with a slide transition. One card per field (when, calendar, location,
description, attendees, recurrence) with leading icons; location taps open
a maps intent. Loading/Failure/Success throughout.

Recurrence is humanized from the RRULE — e.g. "Every week on Tue and Thu
until 31 Dec 2026" — covering FREQ/INTERVAL/BYDAY/UNTIL/COUNT with
abbreviated, italicised day names and localized list formatting, falling
back to a generic label for rules it can't render.

Also:
- fix: recurring events failed to open (series row stores DURATION, not
  DTEND, so the mapper dropped them as EventNotFound). The detail keeps
  them and shows the tapped occurrence's own times from Instances.
- feat: month day cell → opens the day view anchored to that date.
- build: add material-icons-extended (R8 strips unused icons in release).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

app/src/main/java/de/jeanlucmakiola/calendula/ui/CalendarHost.kt

@@ -1,15 +1,27 @@
 package de.jeanlucmakiola.calendula.ui
 
+import androidx.compose.animation.AnimatedVisibility
+import androidx.compose.animation.fadeIn
+import androidx.compose.animation.fadeOut
+import androidx.compose.animation.slideInHorizontally
+import androidx.compose.animation.slideOutHorizontally
+import androidx.compose.foundation.layout.Box
+import androidx.compose.foundation.layout.fillMaxSize
 import androidx.compose.runtime.Composable
 import androidx.compose.runtime.getValue
 import androidx.compose.runtime.mutableStateOf
+import androidx.compose.runtime.remember
 import androidx.compose.runtime.saveable.rememberSaveable
 import androidx.compose.runtime.setValue
 import androidx.compose.ui.Modifier
+import de.jeanlucmakiola.calendula.domain.EventInstance
 import de.jeanlucmakiola.calendula.ui.common.CalendarView
+import de.jeanlucmakiola.calendula.ui.common.rememberCalendarSlideSpec
 import de.jeanlucmakiola.calendula.ui.day.DayScreen
+import de.jeanlucmakiola.calendula.ui.detail.EventDetailScreen
 import de.jeanlucmakiola.calendula.ui.month.MonthScreen
 import de.jeanlucmakiola.calendula.ui.week.WeekScreen
+import kotlinx.datetime.LocalDate
 
 /**
  * Holds the active top-level view (spec M1) and swaps between the calendar
@@ -21,21 +33,69 @@ fun CalendarHost(modifier: Modifier = Modifier) {
     var view by rememberSaveable { mutableStateOf(CalendarView.Month) }
     val onSelectView: (CalendarView) -> Unit = { view = it }
 
-    when (view) {
-        CalendarView.Week -> WeekScreen(
-            selectedView = view,
-            onSelectView = onSelectView,
-            modifier = modifier,
-        )
-        CalendarView.Day -> DayScreen(
-            selectedView = view,
-            onSelectView = onSelectView,
-            modifier = modifier,
-        )
-        CalendarView.Month -> MonthScreen(
-            selectedView = view,
-            onSelectView = onSelectView,
-            modifier = modifier,
+    // Tapping a day in the month grid opens the day view anchored to that date.
+    var pendingDayIso by rememberSaveable { mutableStateOf<String?>(null) }
+    val onOpenDay: (LocalDate) -> Unit = { date ->
+        pendingDayIso = date.toString()
+        view = CalendarView.Day
+    }
+
+    // The event-detail screen (S4) is a full-screen destination hoisted here so
+    // it overlays whichever calendar view is active. We forward the tapped
+    // occurrence's own times (eventId + begin + end, packed as a saveable
+    // long[]) so recurring events show the correct date, not the series start.
+    // [heldKey] keeps the last shown key alive through the slide-out (when
+    // [detailKey] is cleared); it is set in the tap callback — never a [0,0,0]
+    // placeholder — so the destination never loads a bogus id=0 on first frame.
+    var detailKey by rememberSaveable { mutableStateOf<LongArray?>(null) }
+    var heldKey by remember { mutableStateOf<LongArray?>(null) }
+    val onEventClick: (EventInstance) -> Unit = { event ->
+        val key = longArrayOf(
+            event.eventId,
+            event.start.toEpochMilliseconds(),
+            event.end.toEpochMilliseconds(),
         )
+        heldKey = key
+        detailKey = key
+    }
+
+    val slideSpec = rememberCalendarSlideSpec()
+
+    Box(modifier = modifier.fillMaxSize()) {
+        when (view) {
+            CalendarView.Week -> WeekScreen(
+                selectedView = view,
+                onSelectView = onSelectView,
+                onEventClick = onEventClick,
+            )
+            CalendarView.Day -> DayScreen(
+                selectedView = view,
+                onSelectView = onSelectView,
+                onEventClick = onEventClick,
+                initialDateIso = pendingDayIso,
+            )
+            CalendarView.Month -> MonthScreen(
+                selectedView = view,
+                onSelectView = onSelectView,
+                onOpenDay = onOpenDay,
+            )
+        }
+
+        // Prefer the live key; fall back to the held one only while sliding out.
+        val activeKey = detailKey ?: heldKey
+        AnimatedVisibility(
+            visible = detailKey != null,
+            enter = slideInHorizontally(slideSpec) { it } + fadeIn(),
+            exit = slideOutHorizontally(slideSpec) { it } + fadeOut(),
+        ) {
+            activeKey?.let { key ->
+                EventDetailScreen(
+                    eventId = key[0],
+                    beginMillis = key[1],
+                    endMillis = key[2],
+                    onBack = { detailKey = null },
+                )
+            }
+        }
     }
 }